Electrophysiological Studies at Exercise in Patients with Accessory Atrioventricular Pathways
14 patients, 7 with bidirectional, 7 with unidirectional retrograde atrioventricular (A V) conduction through an AV accessory pathway, were submitted to bicycle exercise test from 20 to 140 watts, with 6 minutes and 30 watts steps. Left atrium was paced through a temporary coronary sinus quadripolar electrode. Measurements were done in the supine, sitting position and for each step of the exercise: 1. Atrial (ARP), Kent (KRP) and A V nodal (NPR) effective refractory periods (ERP) on spontaneous rate, and when possible on paced rate at 90 and 130/mn. 2. Shortest atrial cycle conducted 1/1 to the ventricles. 3. AV conduction time in sinus rhythm and orthodromic tachycardia, and VA time in orthodromic tachycardia. Results: 1. ERP constantly shortened with exercise: At 80 watts, compared to the supine values, ARP decreased 62 ± 30 ms, KRP 94 ± 19 ms, NRP 68 ± 34 ms. The shortest 1/1 A V cycle conducted through the A V node shortened 85 ± 31 ms, and 60 ± 25 ms through the Kent bundle. 2. Kent conduction time did not change in an appreciable way. AV nodal conduction time constantly shortened in sinus rhythm (40 ms at 80 watts) as in orthodromic tachycardia (95 ± 10 ms at 110 watts). It explains less marked preexcitation in sinus rhythm, and faster heart rate in orthodromic tachycardia at exercise. 3. These data show the importance of humoral factors on refractory periods and conduction times. They have to be considered when only supine provocative techniques are used to assess effectiveness of anti-arrhythmic therapy.
KeywordsCatheter Depression Peri Fibril Cardiol
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